For all the recent focus on campus sexual assault, new federal numbers show the risk on campuses is still lower than it is for non-students. And the report casts some doubt on a statistic we've heard a lot - that 1 in 5 college students are raped or sexually assaulted. NPR's Tovia Smith has more.

TOVIA SMITH, BYLINE: Much of the federal data confirms what was already known - that most sexual assaults never get reported to police. Only 20 percent of student victims report. It's a bit higher for non-students in the same age range of 18-24. But Lynn Langton from the Bureau of Justice Statistics says the top two reasons are the same for everyone.

LYNN LANGTON: About a quarter of folks say that they didn't report because the incident was a personal matter. And about 20 percent said that they were afraid. They were afraid to report.

SMITH: For most, it was a fear of reprisal. The data also shows 6 of every 1,000 students are victims. It's just over seven per thousand for non-students. Those numbers include victims of completed and attempted assaults, as well as victims of threats. The methodology behind today's report makes it hard to compare to other data, but Northeastern University criminologist James Fox says these government numbers do paint a different picture than the oft-cited statistic that 1 in 5 college students are raped.

JAMES FOX: That statistic we hear over and over and over again - that number has to be taken not just of with a grain of salt, but perhaps the entire saltshaker. And now the Bureau of Justice Statistics has cast even greater doubt.

SMITH: Privately, some advocates say they're concerned about this report coming at the same time that questions are being raised about a Rolling Stone account of an alleged campus rape. They worry it'll give ammunition to those who want to sweep campus sexual assault under the rug. Scott Berkowitz, head of the national advocacy group RAINN, agrees that the 1 in 5 statistic is probably too high. But he says it'd be wrong to conclude that sexual assault is not a problem.

SCOTT BERKOWITZ: However, you slice the numbers, there are an enormous number of victims each year. So there's still a big problem that we need to fix.

SMITH: And that means on-campus and off, Berkowitz says, given that the government data shows sexual assault is an even bigger problem for non-students.

BERKOWITZ: That makes it that much more important that we fix the criminal justice system so that more victims are comfortable reporting and can use it to get justice. We have to make sure we don't leave out the people who don't make it to college.